For example, Patent Document 1 (identified below) discloses an RFID (Radio-Frequency IDentification) tag that includes an RFIC (Radio-Frequency Integrated Circuit) module having a spiral coil formed on a silicon substrate; and a sheet-shaped antenna base material mounted with the RFIC module and having an antenna. The coil of the RFIC module and the antenna of the antenna base material are connected to each other via electromagnetic field coupling, and hence there is no need for DC connection using soldering, etc. For that reason, even though the RFID tag is used under sever conditions causing repetitive deformations, for example, even if it is attached to linen subjected to repetitive washing, connection between the RFIC module and the antenna can be maintained.
Patent Document 1: JP2008-310453A.
With regard to the RFID tag described in Patent Document 1, the coil of the RFIC module and the antenna are electromagnetic field coupled together. Therefore, in order to obtain desired communication characteristics of the RFID tag without variations, the RFIC module needs to be mounted on the antenna base material without variations at a certain position and posture. Particularly, in the case of the RFID tag described in Patent Document 1, since the spiral coil is formed in one surface of the silicon substrate, if the RFIC module is mounted upside down on the antenna base material, the communication characteristics, i.e. the degree of coupling between the coil and the antenna varies to a great extent.